function plot(S1G)
% plot grid

if S1G(1).periodic
	rho = (S1G.points - S1G.min)*2*pi/(S1G.max-S1G.min);
	theta = repmat(pi/2,1,length(rho));
	plot(sph2vec(theta,rho),strtrim(cellstr(num2str(S1G.points(:)))));
else
	y = ones(1,1,GridLength(S1G));
	plot(S1G.points,y,'.','MarkerSize',10);
end
